import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Queue;

public class BinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode node1 = new TreeNode('A');
        TreeNode node2 = new TreeNode('B');
        TreeNode node3 = new TreeNode('C');
        TreeNode node4 = new TreeNode('D');
        TreeNode node5 = new TreeNode('E');
        TreeNode node6 = new TreeNode('F');
        TreeNode node7 = new TreeNode('G');
        TreeNode node8 = new TreeNode('H');

        node1.left = node2;
        node1.right = node3;
        node2.left = node4;
        node2.right = node5;
        node5.right = node8;
        node3.left = node6;
        node3.right = node7;

        return node1;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        System.out.print(root.val+" ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        inOrder(root.left);
        System.out.print(root.val+" ");
        inOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val+" ");
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    void size(TreeNode root) {
        if (root == null) {
            return;
        }
        if (root != null) {
            nodeSize++;
        }
        size(root.left);
        size(root.right);
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if(root == null) {
            return 0;
        }
        return size2(root.left) + size2(root.right) + 1;
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    void getLeafNodeCount1(TreeNode root) {
        if (root == null) {
            return;
        }
        if (root.left == null && root.right == null) {
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if (root ==null) {
            return 0;
        }
        if (root.left == null && root.right == null) {
            return 1;
        }
        return getLeafNodeCount2(root.left) +
                getLeafNodeCount2(root.right);
    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if (root == null) {
            return 0;
        }
        if (k == 1) {
            return 1;
        }
        return getKLevelNodeCount(root.left,k - 1) +
                getKLevelNodeCount(root.right,k - 1);
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if (root == null) {
            return 0;
        }
        return Math.max(getHeight(root.left),getHeight(root.right)) + 1;
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if (root == null) {
            return null;
        }
        if (root.val == val) {
            return root;
        }
        TreeNode leftFind = find(root.left, val);
        if (leftFind != null) {
            return leftFind;
        }
        TreeNode rightFind = find(root.right, val);
        if (rightFind != null) {
            return rightFind;
        }
        return null;
    }


    ArrayList<ArrayList<Character>> list = new ArrayList<>();

    //层序遍历
    void levelOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        int level = this.getHeight(root);
        for (int i = 0; i < level; i++) {
            this.list.add(new ArrayList<>());
        }
        addNode(root,0);
        for (int i = 0; i < level; i++) {
            ArrayList<Character> list1 = list.get(i);
            for (int j = 0; j < list1.size(); j++) {
                System.out.print(list1.get(j)+" ");
            }
        }
        System.out.println();
    }
    void addNode(TreeNode root,int nowLevel) {
        if (root == null) return;
        list.get(nowLevel).add(root.val);

        addNode(root.left,nowLevel+1);
        addNode(root.right,nowLevel+1);
    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if(root == null) {
            return true;
        }
        //创建队列 添加根节点
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        //当cur不为空时，添加其左右孩子
        TreeNode cur = root;
        while (cur != null) {
            cur = queue.poll();
            if (cur != null) {
                queue.offer(cur.left);
                queue.offer(cur.right);
            }
        }
        //cur为空时，判断队列中是否有非空元素
        //若剩余元素全为null则说明该树为完全二叉树；
        // 若剩余元素存在非null元素则说明该树不为完全二叉树。
        boolean flg = false;
        while (!queue.isEmpty()) {
            TreeNode cur2 = queue.poll();
            if (cur2 != null) {
                flg = true;
            }
        }
        if (flg == true) {
            return false;
        }else {
            return true;
        }
    }
}